1. Field of the Invention
The invention relates to vacuum cleaners, and in particular to a cyclone separator for a vacuum cleaner. In one of its aspects, the invention relates to a vacuum cleaner with a fine contaminant separator for removing fine contaminants from the working air.
2. Description of the Related Art
Cyclone separators are well known. Some follow the textbook examples using frustoconical shaped separators and others use high-speed rotational motion of the dir-laden air to separate the dirt by centrifugal force. Separation of the dirt/dust from the air is not difficult, but the problem of keeping the dirt separated from the airflow has not been adequately solved. There is a tendency for the separated debris to re-entrain into the airflow and thereby pass through the separator or for fine particles/contaminants to remain in the airflow after passing through the cyclone separator. Some minor amounts of fine dust usually pass through the cyclone and are filtered in secondary filters located downstream of the cyclone separator to maximize dust removal. These filters are positioned anywhere from the cyclone exit port to the clean air exhaust port.
The U.S. Pat. No. 6,440,197 to Conrad attempts to solve the re-entrainment problem by placing an apertured particle separation member near the bottom of the cyclonic chamber. In this case, the apertured particle separation member allows the fine particles in the cyclonic airstream to pass through the apertures and come to rest in a relatively dead zone beneath the cyclone chamber. However, as larger particles of dirt collect on top of the separation member, the fine particles cannot pass through the apertured particle separation member into the dead zone. As a result, the fine particles are not separated from in the airstream and are eventually trapped in a downstream filter.
The U.S. Pat. No. 6,221,134 to Conrad et al. discloses another attempt to separate fine particles of dirt from a cyclonic air flow in a cyclone separator. Conrad et al. 134 discloses a fine particle-receiving chamber beneath the cyclonic fluid flow region. The fine particle-receiving chamber is formed beneath a particle-separating plate that extends across the width of the separator chamber and has a plurality of narrow slots sized for passing the fine particles from the separator chamber to the fine particle-receiving chamber. However, this separator plate has a problem similar to that found in the Conrad 197 patent; as large particles of dirt collect on the particle-separating plate, the larger particles block the path of the fine particles, with the result that a significant amount of fine particles cannot pass through the separator plate and remains in the cyclonic air flow.
The U.S. Pat. No. 6,344,064 to Conrad et al. discloses yet another attempt to separate fine particles from the airflow by utilizing a plurality of secondary cyclones arranged in parallel downstream of a primary upstream cyclone. A downstream particle collector is provided for the downstream cyclones, and the upstream cyclone has it own corresponding upstream particle collector. The particle collectors are configured such that the downstream particle collector is emptied when the upstream particle collector is emptied. Alternatively, the downstream particle collector can be emptied into the upstream particle collector whereby all of the particles are emptied through the upstream particle collector.
U.S. Pat. No. 6,810,557 to Hansen et al. discloses an upright vacuum cleaner that has a cyclone separator and a dirt cup. A horizontal plate separates the cyclone separator from the dirt cup. The air flowing through the cyclone separator passes through an annular cylindrical cage with baffles and through a cylindrical filter before exiting the cyclone separator at the upper end thereof. The dirt cup has three finger-like projections extending upwardly from the bottom thereof to agglomerate the dirt in the dirt cup. The dirt cup further has a pair of radial fins extending inwardly from the sidewalls of the dirt cup. The U.S. Patent Application Publication No. 20030159411 to Hansen et al. discloses a cyclone separator comprising a dirt separation module having a separator plate between the cyclone region and the dirt collection region. The separator plate has an outer diameter smaller than the inner diameter of the cylindrical wall of the dirt separation housing so that a gap separates the outer edge of the separator plate and the inner wall of the dirt tank. The U.S. Patent Application No. 60/481,542, filed Oct. 22, 2003, discloses a cyclone separator comprising a cyclone exhaust airflow directed through a fluid conduit positioned in the center of the cyclone region. Cyclone exhaust airflow passes through a filter chamber below the dirt collection region before entering the motor fan inlet.